Currently, replacement of a malfunctioning heart valve is accomplished by a major open-heart surgical procedure requiring general anesthesia, full cardio-pulmonary bypass with complete cessation of cardio-pulmonary activity, and a long period of hospitalization and recuperation. In most cases, the native valve is resected (cut-out) and the replacement valve then installed.
The appropriate size replacement valve is determined using plugs. The surgeon chooses a plug from a tray of plugs increasing in size by 1 mm increments or so. If the chosen plug is too loose in the patient's aorta, a larger plug is chosen; if the plug chosen is to large to fit in the patient's aorta, a smaller plug is chosen, and so on until the chosen plug fits just right. Then, a replacement valve of a size corresponding to the size of the correct plug is installed and stitched in place. As can probably be ascertained, the use of plugs to correctly size the replacement valve results in a time consuming and somewhat inexact procedure.
As an alternative to open heart surgery, those skilled in the art have attempted to devise systems for endovascular heart valve replacement to overcome the disadvantages associated with open-heart surgery. U.S. Pat. No. 5,370,685, for example, discloses a procedure device capsule connected to a tube and delivered to the site via a guide wire introduced in the femoral artery of a patient. The device capsule houses an expandable barrier attached to balloon segments. Once the guide wire is removed and the barrier is expanded, a tissue cutting blade assembly is advanced in the tube and rotated by a DC motor to resect the existing valve. The barrier traps any debris cut by the tissue cutting blade assembly. Tissue is then suctioned out via the tube. Next, the cutting blade assembly is removed, the barrier balloons are deflated, and the barrier is brought back into the capsule and the capsule itself is removed.
Then, a valve introducer capsule is advanced to the situs. The capsule houses a replacement valve and includes a pusher disk and inflatable balloon segments. After the balloon segments are inflated, the pusher disk pushes the replacement valve into position and a mounting balloon is used to expand the replacement valve and to secure it in place. Then, the introducer capsule is removed. The '685 patent is hereby incorporated herein. See also U.S. Pat. Nos. 5,545,214; 6,168,614; 5,840,081; 5,411,552; 5,370,685; and published U.S. Patent Application No. 2002/0058995 A1. These patents are also incorporated herein.
Other relevant art includes the following, also included herein by this reference. Published U.S. Patent Application No. 2002/0095116 A1 discloses an aortic filter, an artery filter, and a check valve attached to the distal end of a canula for resecting an aortic valve from within the aorta. U.S. Pat. No. 6,287,321 also discloses a percutaneous filtration catheter. U.S. Pat. No. 5,554,185 discloses an inflatable prosthetic cardiovascular valve. U.S. Pat. No. 6,425,916 discloses a percutaneous approach with a valve displacer for displacing and holding the native valve leaflets open while a replacement valve is expanded inside the native valve. In this way, the native valve does not need to be resected.
One problem with the percutaneous approach, however, is that conventional plugs can no longer be used to correctly size the replacement valve. And, the art discussed above fails to teach or suggest any alternative sizing mechanism.